Wrong status icons showing on subfolders set to online only on Windows

OK, so I have found the problem. It seems there is a hard limit on the number of subfolders allowed in any parent folder.

As a test, I created a new folder called Yr 2021 set it to online only, and started copying folders, a few at a time from Year 2021 to Yr 2021. Everything was going well at first, then suddenly, the icon on Yr 2021 changed to the green "Available on this device" icon. I tried looking through the last few folders I copied, but could not see anything out of place there. So I started transferring them back, and after a few copies, the icon swapped back to the correct one. I tried just adding "New folder" subfolders, and as soon as I hit 250, the icon switched to the wrong one. It seems the hard limit is 249 subfolders. Anything over that and the wrong icon is displayed.

First I tried putting three subfolders inside Year 2021 and transferred about 200 folders into each subfolder. That didn't work, so I renamed Year 2021 to Year 2021-1, and created three new folders, Year 2021-2, Year 2021-3 and Year 2021-4. I then distributed all the folders (about 700 altogether among those three folders. That worked, and all four folders showed the correct icon. Of course, the Parent folder "Film Archive" shows the wrong icon, because it contains a lot more subfolders.

A hard limit on subfolders is probably not a good idea and needs addressing. Windows has no limit on the number of subfolders in a parent folder (nor does MacOS) and nor should Dropbox.

What I have done is a workaround - an end-run around the problem. It is not a solution, and should not be regarded as such. It is something that needs addressing.